1. Field of the Invention
The present invention pertains generally to an apparatus and method for manufacturing components for implantable medical devices such as batteries or capacitors. More particularly, the present invention relates in one embodiment to thermal encapsulation of a battery or capacitor electrode within a protective polymer film.
2. Description of Related Art
Devices for heat sealing a variety of objects within thermoplastic films are generally known. Additionally, the sealing of capacitor and battery electrodes within thermoplastic films is also known. The encapsulation of an electrode within a porous polymer film is also known. The film provides a physical separation between the electrode, and an associated opposite polarity electrode, thereby preventing a short circuit between the electrodes.
Conventional thermal encapsulation systems generally are capable of cutting and sealing low melting point thermoplastic polymers such as polypropylene, but are not effective at processing polytetrafluoroethylene (PTFE) and similar high melting temperature fluoropolymers. However, subsequent capacitor or battery manufacturing processes after electrode encapsulation, such as case welding, occur at high temperatures. Low melting polymer separator films can be damaged during these processes, resulting in product that must be scrapped. Additionally, the hard materials and sharp edges of the components used in these systems may damage the separator film during the encapsulation process, or during removal of the encapsulated electrode from the encapsulation apparatus.
There are also no provisions for applying tension to the film to take up slack immediately prior to contact by the heating element of the apparatus, or for accommodating variances in thickness between electrodes being processed. Conventional systems are set up to encapsulate an electrode having the upper limit of the thickness tolerance. This results in some electrodes having encapsulating films that are loosely fitted.
What is needed, therefore, is a thermo-encapsulating apparatus and method that is capable of providing a tight fitting defect-free encapsulation of an electrode in a high melting point thermoplastic material.